I've been having a problem with my Nook Classic in which I no longer can open any side-loaded books and documents. Books from my B&N library still open without a problem.

When I try to open any side-loaded content, however, the Nook gets stuck in the "opening document" mode but never opens the book. I have tried opening the books from the "reading now" button and by going through the library and trying to open the book directly or through the options menu for each book. I updated the firmware from 1.5 to 1.7, have tried turning the Nook on and off numerous times, and have taken out the battery and then rebooted. Nothing has worked.

Has this happened with anyone else? Any other suggestions of what to try next?

Maybe it's one bad document/book that causes the trouble. Try deleting the sideloaded content at reload just one book and see if you can open it. If that works, try loading books a few at a time and see if it works before loading the next chunk. Worth a try anyway.